1. Field of the Invention
The present invention relates to a method of manufacturing an automotive instrument panel having a concealed airbag. More particularly, the present invention relates to a method of forming an airbag-receiving opening in a plastic substrate by imaging a light beam through the substrate and forming a fracturable opening path in the instrument panel.
2. Description of the Related Art
It is known to manufacture an automotive airbag having a seamless covering. One such device is described in U.S. Pat. No. 5,447,328, issued Sep. 5, 1995. The reference teaches a hinged metal door secured to a plastic substrate. The hinge is secured to both the plastic substrate and the metal door and folds when the airbag is inflated. A deep groove directly overlying the perimeter of the metal door forms a weakened section in the covering that tears when the door is opened. An airbag door and cover of this construction is difficult to manufacture because a metal hinge must be secured to only one edge of the plastic substrate. It is also difficult to form a deep groove in the covering that directly overlies the perimeter of the metal door. The groove construction taught in the U.S. Pat. No. 5,447,328 patent extends almost to the surface of the plastic substrate, making it difficult to inject foam in the vicinity of the groove. It is desirable to inject foam between the cover and the door to secure the two components without causing the foam to impede the opening of the door.
It is also known that the rapid force needed to deploy an airbag causes stress on the molded plastic substrate when the door is attached to only one edge. Various frames may be attached to the perimeter of the airbag opening to make the substrate more rigid. An example of this construction is illustrated in U.S. Pat. No. 5,393,088 issued Feb. 28, 1995. A metal frame is secured within the aperture of a plastic substrate. A door is attached to one side of the frame with a hinge. The metal frame keeps the substrate from deforming under the impact of an inflating airbag.
Finally, it is also known to use a laser to score an instrument panel to form a weakening pattern. The laser completely penetrates the substrate and foam and partially penetrates the covering to form the weakening pattern. A method of forming this weakening pattern is described in U.S. Pat. No. 5,744,776 and is incorporated herein by reference. The U.S. Pat. No. 5,744,776 reference teaches bonding the substrate to the covering inside the weakened section. This results in the substrate being positioned in front of the deploying airbag. The rigid plastic substrate must be restrained. It is desirable to form an instrument panel with an aperture in the substrate for the airbag. This eliminates the need to restrain or tether the cutout section of substrate.
It is an advantage of the present invention to provide a seamless airbag covering having a hinged door that is secured to a substrate. It is a further object of the present invention to provide an easily manufacturable method of forming an aperture in the substrate by means of a laser beam by forming a cut-out section that is not adhered to the covering. It is also an advantage of the present invention to provide a method of removing a cutout section of the substrate and forming an airbag-receiving aperture in an instrument panel. The process further includes forming a fracturable opening through the covering in one operation.
These and other problems of the related art are overcome by the present invention.